JPH07220989A - Exposure apparatus and manufacture of device using the same - Google Patents

Abstract

PURPOSE:To immediately sense a malfunction of an illuminance unevenness by providing means for measuring an intensity distribution of an exposure light during real exposing of a wafer. CONSTITUTION:When an exposure operation of one chip exposure area on a wafer 13 is started, a reticle stage 9 and a wafer stage 14 are cooperatively moved in a direction perpendicular to an illuminating direction of an illumination light 7, scanned on a luminous flux of the light 7, and a pattern on a reticle 8 is started to be transferred on a surface of the wafer 13. A photosensor 10 detects the flux of the light 7 during transferring to sequentially measure illuminances corresponding to positions at each predetermined sampling time interval, and its each illumination data is Ui. The illuminance of the light 3 is sequentially detected by an illuminometer 5 at the same time as the time for detecting the illuminance, and its each illuminance data is Li. In order to remove flicker of an illumination light source and influence of aging change of the illuminance, when each illumination ratio value Ii is represented by Ii = Ui/Li, an illuminance distribution curve of the light 7 of the Ii is obtained by executing one exposure operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used when a circuit pattern is printed on a wafer for manufacturing a device such as an integrated circuit, and a device manufacturing method using the same.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the illuminance unevenness of the exposure light of an exposure apparatus, an illuminance measuring device is arranged on the side of the wafer moving means, and a predetermined period of time is set separately from the actual exposure process.
The wafer moving means including the illuminance measuring device is moved within the exposure area of the wafer to detect the illuminance at a plurality of points on the wafer surface, thereby providing time for measuring the illuminance unevenness.

[0003]

However, since the conventional illuminance nonuniformity measurement time is measured in a fixed period other than the actual exposure operation period, even if the illuminance nonuniformity is abnormal during the actual exposure operation period. It cannot be detected immediately.

Further, since the conventional illuminance unevenness measurement requires a constant long time in addition to the actual exposure operation, the throughput of the apparatus is lowered.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure apparatus and a device manufacturing method using the same which solve the above-mentioned conventional problems.

In order to achieve the above object, an exposure apparatus and a device manufacturing method using the same according to the present invention are provided in an exposure apparatus which exposes a wafer through a pattern of a reticle by exposure light during an actual exposure operation on the wafer. It is characterized in that it is provided with means for measuring the intensity distribution (illuminance distribution) of the exposure light. Since the illuminance unevenness is measured during the actual exposure operation, the throughput is increased and an abnormality in the illuminance unevenness can be immediately sensed.

In order to achieve the above object, in a preferred embodiment of an exposure apparatus and a device manufacturing method using the same according to the present invention, the actual exposure is performed by scanning the reticle and the wafer with respect to the exposure light, The measuring means is
It is characterized in that it is provided in a means for moving the reticle. As a result, in addition to the above effects, an effect that the configuration is simple occurs.

Further, a more preferable mode is characterized in that a plurality of light receiving elements for receiving light at both ends of the exposure light are provided in a direction intersecting with a moving direction of the reticle,
It is possible to measure the illuminance unevenness in the direction intersecting the moving direction of the reticle.

In a more preferred form, the measuring means comprises means for comparing the light intensity (illuminance) of each measured point with the light intensity of a predetermined portion of the exposure light, whereby the intensity of the exposure light is increased. It is possible to eliminate measurement errors due to fluctuations.

[0010]

1 is a schematic view of an exposure apparatus according to an embodiment of the present invention. In the figure, 1 is an illumination light source for exposure, 2 is an optical converter that makes illumination light from the illumination light source 1 into a slit shape having a rectangular cross section, and 3 is output from the optical converter 2. The rectangular slit-shaped illumination light serves as the reference light for the illuminance data. Reference numeral 4 denotes a mirror for bending the illumination light 3 and reference numeral 5 denotes an illuminance meter arranged at a position for detecting the illuminance of one point in the illuminance area of the illumination light 3 near the center to obtain the reference value of the illuminance data.

Reference numeral 6 is an optical element in the illumination system, and reference numeral 7 is illumination light in the shape of a slit having a rectangular cross section with which the reticle 8 is irradiated with the illumination light 3 after passing through the optical element 6 in the illumination system. Reference numeral 8 is a reticle, and 9 is a reticle stage that holds the reticle 8. The exposure light 7 scans the reticle by operating in the direction perpendicular to the irradiation direction of the illumination light 7 during exposure.

A photosensor 10 fixed on the reticle stage 9 is arranged outside the illuminance area of the illumination light 7 that scans and irradiates the reticle surface during exposure, and moves (scans) the reticle stage 9 during actual exposure operation. ), The illuminance of the illumination light 7 in the scanning direction is detected at a plurality of points. In this embodiment, one pair (two in total) are arranged in a direction perpendicular to the scanning direction which is the same as the moving direction of the reticle and the wafer.

Reference numeral 11 is a mirror fixed on the reticle stage 9 for guiding the luminous flux of the illumination light 7 to the photo sensor. In the present embodiment, a pair of light beams is arranged at the left and right ends of the illumination light 7 in the vertical direction with respect to the scanning direction within the light flux region, and has a rectangular slit shape during the actual exposure operation. To each photo sensor 10. Reference numeral 12 is a reduction projection optical system, 13 is a wafer onto which the pattern image of the reticle 8 by the illumination light 7 is transferred, and 14 is a wafer stage which holds the wafer 12.

FIG. 2 is an illuminance distribution curve of the illumination light 3.
In the figure, an illuminance distribution curve 101 represents an illuminance change curve of one point in the illumination area of the illumination light 3 over time. Actually, as shown in the figure, the illuminance value is caused by flickering of the illumination light source or aging of the illuminance. Changes from moment to moment. The illuminance distribution curve 102 is a cross-sectional shape of the illuminance distribution on the scanning direction side of the illumination light 7. Further, the illuminance distribution curve 103 is the illumination light 7
3 is a cross-sectional shape of the illuminance distribution in a direction perpendicular to the scanning direction of.

When the reticle stage 9 scans the illumination light 7 after the exposure operation is started, the two left and right photosensors 10 on the reticle stage 9 scan the illumination light 7 in the scanning direction, and the illuminance in FIG. The illuminance like the distribution curve 102 is detected. Further, with respect to the direction perpendicular to the scanning direction of the illumination light 7, the illuminance at two points on the left and right ends of the illuminance distribution curve 103 in FIG. 2 is repeatedly detected.

If there is uneven illuminance at this time, the illuminance distribution curve 1
02 and 103 are distorted curves. That is, taking the illuminance distribution curve 103 of FIG. 2 as an example, it is bilaterally symmetric if the optical mechanism is properly adjusted. However, if the adjustment is not correct, it will be asymmetrical. By detecting the illuminances at the left and right ends of the light flux with the two photosensors 10, it is possible to detect the illuminance unevenness due to the illuminance difference in the direction perpendicular to the scanning direction of the illumination light 7. A large number of photosensors may be arranged to increase the accuracy.

In the present embodiment, as a procedure for measuring the illuminance unevenness, first, when the exposure operation for one chip exposure area on the wafer 13 starts, the reticle stage 9 and the wafer stage 1
4 starts to move in a direction perpendicular to the irradiation direction of the illumination light 7, and scans the luminous flux of the illumination light 7 to start transferring the pattern on the reticle 8 onto the surface of the wafer 13. There is a timing at which the photosensor 10 can detect the luminous flux of the illumination light 7 at one time during the transfer, and the illuminance corresponding to each position is measured at every predetermined sampling time interval t. Each illuminance data by the exposure operation at this time is Ui. In addition, the illuminance of the illumination light 3 is detected by the illuminance meter 5 at the same time as the time when the photo sensor 10 detects the illuminance. Let each illuminance data at this time be Li.

In order to eliminate the influence of the flicker of the light source due to the illumination light source and the change of the illuminance with time, each illuminance ratio value in this exposure operation is set to Li as a reference value and Ii = Ui / Li (1) Represent

By performing one exposure operation, assuming that the number of samplings is N, the illumination light 7 in the scanning direction side corresponds to the illuminance distribution curve 102 of FIG. 2 consisting of N illuminance ratio values Ii. An illuminance distribution curve is obtained.

Here, of these illuminance distribution curves, a reference illuminance distribution curve without unevenness in illuminance is set in advance.
Then, in this reference illuminance distribution curve, each illuminance ratio value at the same time as Ii is set as SIi. The value of the illuminance unevenness at each measurement position of the illumination light 7 at this time is Di = (| Ii-SIi |) / SIi (2).

In addition to the illuminance unevenness, the actual value of Di takes into consideration the illuminance deterioration caused by the optical element 6 that generates the illumination light 7. If Ii has uneven illuminance and there is no illuminance deterioration, the values of Ii and SIi are the same, and Di = 0.

Further, the exposure apparatus is set in advance with an allowable value MAX (Di) of each illuminance unevenness that affects the actual exposure operation. Generally, the uneven illuminance value does not change rapidly, but gradually changes as the long-time exposure operation is repeatedly executed.

Here, when Di> | MAX (Di) -Ki-Ji | (Ki is a constant value at each measurement position) (Ji is the illuminance deterioration amount at each measurement position), the illuminance unevenness approaches the allowable value. Predicting that
Immediately during the exposure operation, the exposure apparatus is informed accordingly.

Further, the illuminance values of the illumination light 7 at the two left and right ends of the light beam 7 are simultaneously obtained by one-to-two photosensors on the left and right sides in one exposure operation. The left and right illuminance data resulting from the exposure operation at this time are Uli and Uri, respectively. At this time, the illuminance values at the right and left ends of the illuminance distribution curve in the direction perpendicular to the scanning direction of the illumination light 7 that corresponds to the illuminance distribution curve 103 in FIG. 2 are obtained.

Next, similarly to the above formula (1), the illuminance ratio values at the two right and left ends are set with Li as a reference value, Ili = Uli / Li (3) Iri = Uri / Li. It is represented by (4).

Here, the difference Ei between the two is taken, and Ei = | Ili-Iri | (5), and this value is taken as the value of uneven illuminance. If there is no unevenness in illuminance, the difference Ei between the left and right illuminance ratio values by the photosensor 10 is Ei = 0.

Here, the allowable value MAX (Ei) which affects the actual exposure operation is set in advance in the exposure apparatus.
That is, if Ei> | MAX (Ei) -Mi | (6) (where Mi is a constant value at each measurement position), the illumination light 7
It is predicted that the illuminance value of is approaching the allowable value, and the exposure apparatus is immediately notified during the exposure operation. When the exposure apparatus receives the notification that the value Di or Ei of the uneven illuminance is outside the allowable value, it notifies the operator of this situation and interrupts the exposure operation. Further, the exposure apparatus of the present invention can be used with a function of notifying the operator without interrupting the exposure operation by making a specific setting in advance from an operation console (not shown). ing.

Outside the wafer 13 on the wafer stage 14, a sensor element array for illuminance unevenness measurement is arranged along the scanning direction to cover the exposure area length (slit width),
When obtaining the intensity distribution in the scanning direction of the light irradiating the wafer 13 before and after the actual exposure (that is, the illuminance distribution on the wafer 13),
The photo sensor 10 on the reticle stage can be used.

When measuring the light intensity distribution with the sensor element array, the illuminance distribution curve cannot be accurately drawn unless the variation in the sensitivity between the sensor elements is corrected. Therefore, the mirror 11 on the reticle stage is set to a half mirror, and the reticle stage 9 is moved to move the photo sensor 10
Is positioned at a position corresponding to the position of each sensor element, and the sensor element array detects the transmitted light from the half mirror while detecting the reflected light from the half mirror by the photo sensor 10, and the output of the photo sensor 10 is used as a reference. As a result, the variation in sensitivity between the sensor elements is measured.

[0030]

According to the present invention, the illuminance unevenness can be measured during the actual exposure operation, and therefore, it can be immediately detected that the illuminance unevenness exceeds the allowable value. Therefore, it is possible to prevent defects in the exposure pattern on the wafer in the subsequent exposure. Further, it is possible to omit the measurement of the illuminance unevenness in the steps other than the actual exposure step, and there is an effect that the throughput of the apparatus is not reduced.

[Brief description of drawings]

FIG. 1 is a main schematic diagram of an exposure apparatus embodying the present invention.

FIG. 2 is an illuminance distribution diagram of illumination light having a slit shape.

[Explanation of symbols]

 1 Illumination Light Source 2 Optical Converter 3 Illumination Light 4 Mirror 5 Illuminometer 6 Illumination System Optical Element 7 Illumination Light 8 Reticle 9 Reticle Stage 10 Photosensor 11 Mirror 12 Reduced Projection Optical System 13 Wafer 14 Wafer Stage

Claims (6)

[Claims] 1. An exposure apparatus for exposing a wafer with exposure light through a pattern of a reticle, comprising means for measuring an intensity distribution (illuminance distribution) of the exposure light during an actual exposure operation on the wafer. Exposure equipment. 2. The exposure apparatus according to claim 1, wherein the actual exposure is performed by scanning the reticle and the wafer with respect to the exposure light. 3. The exposure apparatus according to claim 2, wherein the measuring unit is provided in a unit that moves the reticle. 4. The exposure apparatus according to claim 2, wherein the measuring unit includes a plurality of light receiving elements that receive light at both ends of the exposure light in a direction intersecting a moving direction of the reticle. 5. The exposure apparatus according to claim 1, wherein the measuring means includes means for comparing the light intensity (illuminance) of each measured point with the light intensity of a predetermined portion of the exposure light. 6. A device manufacturing method, comprising the step of transferring a device pattern onto a substrate by the exposure apparatus according to claim 1.